In response to the rapid development of mobile communication and Internet technologies and various requirements of subscribers, recent mobile communication services have reached a stage capable of providing not only the conventional voice communication service but also a high speed packet service which enables transmission of large capacity digital data including an e-mail or a still image through a mobile communication terminal. As a result, mobile communication systems are evolving from the voice-based Circuit Switched (CS) domain to a packet-based Packet Switched (PS) domain.
The Core Network (CN) for providing a multimedia service through the Internet has changed from the existing line-based core network into a packet-based core network, and is further evolving into an Internet Protocol (IP) based core network. A communication system which provides an IP multimedia service to subscribers through an IP based core network is called an IP Multimedia Subsystem (IMS). In the 3rd Generation Partnership Project (3GPP)/3GPP2, various researches for smoothly providing all IP services through an IMS are in progress.
Meanwhile, a mobile communication system establishes a Policy and Charging Control rule (hereinafter, referred to as “PCC rule”) for service quality policies and use of services, and provides a service to terminals according to the established PCC rule. In other words, the Policy and Charging Control (PCC) corresponds to a technology of recognizing a type of a service and determining a service quality (Quality of Service; QoS) and a charging policy proper for the service. Entities playing an important role in a PCC structure include a Policy and Charging Rules Function (PCRF) and a Policy and Charging Enforcement Function (PCEF).
The PCRF corresponds to a device for dynamically applying QoSs and charging policies discriminated according to services and determines the PCC rule based on information on a service and information on a user. The PCEF detects a service provided to a user, receives a PCC rule from a PCRF for charging control and QoS of the detected service, applies a QoS policy discriminated for each service based on the PCC rule received from the PCRF, and then generates charging information according to the QoS policy. That is, the PCRF transmits a command message to the PCEF, so as to establish a new PCC rule for the PCEF or amend or remove an already established PCC rule.